Congressional criticism of President Bush’s troop surge in Iraq threatens to erode the morale of American soldiers and Marines serving there, Sen. John McCain (R-Ariz., pictured), implied Tuesday at the Senate confirmation hearing for Army Lt. Gen. David Petraeus, Bush’s choice to be the new commander in Iraq.

MSNBC reports that McCain’s raising of the morale question was quickly disputed by one of his potential 2008 presidential rivals, Sen. Hillary Clinton (D-N.Y.).

Clinton and McCain may get a chance to put their clashing ideas to the test of the electorate in the 2008 presidential election: polls show the pair as the leading contenders for nominations of their respective parties.

McCain raised the morale issue in a question he posed to Petraeus:

“Suppose that we send additional troops and we tell those troops, ‘we support you, but we are convinced you cannot accomplish your mission… we do not support the mission we are sending you on’? What effect does that have on morale of the troops?”

“It would not be a beneficial effect, sir,” Petraeus answered.

Clinton disagreed with both John McCain and Petraeus on the morale issue.

“Our troops are on the Internet constantly; they know very well there’s a debate going on in this country,” Clinton told reporters after she left the Armed Services Committee confirmation hearing. “From the troops I’ve spoken with, a lot of them share many of the concerns that I and others have.”

In his opening statement to the committee, Petraeus addressed the need for support from the American people in order for Bush’s effort to stabilize Iraq to succeed.

“We face a determined, adaptable, barbaric enemy. He will try to wait us out,” the general said, calling the struggle in Iraq “a test of wills.”

Despite her criticism of Bush for sending the 21,500 into the Iraq war, Clinton told reporters she would not vote against the Petraeus nomination as a way to express her opposition to the surge idea.

“The president is going forward with this policy; this debate is academic,” she said with a note of resignation in her voice.

“I want the very best leadership for the young men and woman who are going to be put into harm’s way to implement this strategy and I have no doubt Gen. Petraeus is the person to try to pull this off,” Clinton said.

She has called for limiting the number of U.S. troops in Iraq to the number of troops that were there on New Year’s Day. She also wants to require Bush to seek congressional authorization for any additional troops.

“I do not support cutting funding for American troops,” Clinton said last week, noting that she opposes a specific deadline for getting U.S. forces out of Iraq.

The former First Lady has also said she supports a non-binding resolution offered by Sens. Joe Biden (D- Del.), Carl Levin (D-Mich.), and Chuck Hagel (R-Neb.), which voices disapproval of Bush’s deployment of additional troops — which it refers to as “escalating” the U.S. presence in Iraq.

Sens. John Warner (R-Va.), Susan Collins (R-Me.) and Ben Nelson (D-Neb.), have offered their own non-binding resolution of disapproval, but it does not use the word escalating, which some Republican critics of the war find inflammatory.

McCain vehemently opposes non-binding resolutions and the idea of putting a cap on troops in Iraq. The Arizona Republican got strong support in his use of the morale issue from allies Sen. Joe Lieberman, independent Democrat from Connecticut, and Sen. Lindsey Graham (R-S.C.).

Taking a shot at Clinton and other critics of Bush’s policy on the morale question, McCain made clear his own criticism of Bush and his advisors on how they’ve conducted the war so far.

He said the 21,500 troops being sent in President Bush’s announced increase “are either inadequate or barely minimal.”

As Clinton and others pointed out Tuesday, the troop-to-civilian population ratio after the troop surge will fall well short of the proposed ratio in the counter-insurgency doctrine that Petraeus himself issued as commander of the army’s think tank at Fort Leavenworth, Kansas.